1. Field of the Invention
The present invention generally relates to a contactor for testing a semiconductor device and, more particularly, to a contactor for testing an LSI (Large Scale Integration) circuit having fine terminals or terminals arranged with a fine pitch and a manufacturing method of the contactor.
In testing a semiconductor device such as an LSI circuit during a manufacturing process thereof, a contactor is used for making electrical contact with a terminal of the LSI circuit. In testing a conventional semiconductor device having a socket for connection, the socket can be used as a contactor. However, an LSI circuit, such as a so-called KGD (Known Good Die), which is to be tested as a bare chip not yet packaged, or a CSP (Chip Size Package), does not have a socket. Therefore, a contactor for test use needs to be prepared for such an LSI circuit.
Recently, a wafer-level packaging technology has been developed, which technology allows for packaging a semiconductor chip in the form of a wafer. This calls for testing of a plurality of semiconductor devices in the form of a wafer. Therefore, it is desired that a low-cost testing contactor be developed, which contactor can be easily manufactured and is usable for such testing.
2. Description of the Related Art
Tests using contactors include a burn-in test and such a final test as a high-speed test.
Since a burn-in test requires a long period of time for its process, in a wafer-level testing, all of LSI circuits on a wafer need to be tested at one time. To realize this, terminals of all of the LSI circuits on the wafer need to be put into contact with probes, and wires connected to the probes need to be drawn out to the exterior by a test board (burn-in board). Such a burn-in board has to have tens of thousands of terminals.
Since the burn-in test puts an LSI circuit under a high-temperature condition (ranging from 125° C. to 150° C.), a testing contactor has to have high heat resistivity. It has conventionally been very difficult to realize a contactor which fulfills these requirements, and if the contactor could be realized, the contactor would be extraordinarily costly and have a short life duration.
To conduct a high-speed test in the form of a wafer as a final test, a length of a probe of a contactor has to be smaller. That is, since the length of the probe is substantially proportional to the impedance of the contactor, the high-speed test cannot be performed with the increased impedance of a contactor having a long probe. Therefore, the probe of a contactor used in the high-speed test has to be as short as possible.
As in the burn-in test, in order to test a plurality of semiconductor devices at one time, a multitude of probes have to be arranged close to one another. It has conventionally been very difficult to realize a contactor which fulfills these requirements, and if it could be realized, the contactor would be extraordinarily costly.
FIG. 1 is a cross-sectional view of a part of a conventional contactor using an anisotropic conductive elastomer. The contactor shown in FIG. 1 uses an anisotropic conductive rubber 2 as an anisotropic conductive elastomer. The anisotropic conductive rubber 2 is disposed between an LSI circuit 6, a testee, and a test board 8. The test board 8 has electrodes 8a to be electrically connected to terminals 6a of the LSI circuit 6.
A membrane 4 is disposed between the anisotropic conductive rubber 2 and the LSI circuit 6 in order to ensure contacts between the anisotropic conductive rubber 2 and the terminals 6a of the LSI circuit 6. Therefore, the membrane 4 is unnecessary if the contacts can be ensured without it. In addition, although FIG. 1 shows the terminals 6a of the LSI circuit 6 formed on concave portions, the terminals 6a do not necessarily have to be formed on the concave portions, but may be formed on a flat surface.
The anisotropic conductive rubber 2 is arranged to have conductive portions 2b and other insulating portions. Accordingly, each of the terminals 6a of the LSI circuit 6 is electrically connected to the corresponding electrode 8a. In this structure, an elasticity of the anisotropic conductive rubber 2 ensures a contact pressure between each of the terminals 6a of the LSI circuit 6 and the corresponding electrode 8a of the test board 8.
The above-mentioned contactor using an anisotropic conductive rubber has a simple structure and is often used in conventional wafer-level testing. The anisotropic conductive rubber has an advantage of having a small inductance. Also, the anisotropic conductive rubber, when deteriorated or damaged, can be replaced, independent of a test board.
Aside from the above-mentioned contactor using an anisotropic conductive material, there is a contactor using a spring-type contact pin. FIG. 2 is a side view of a part of a conventional contactor using a spring pin.
The contactor shown in FIG. 2 has bent wires 10 as probes (contact pins) on a test board 12. Such a bonding wire as a gold wire is used as the wire 10. The wire 10 is formed by a wire bonder. Specifically, the wire 10 is severed after one end of the wire 10 is bonded to an electrode 12a of the test board 12 and is bent as shown in FIG. 2. The bent parts enable the wire 10 to deform elastically in a direction perpendicular to a plane of the test board 12. Pressing the other end of the wire 10 against the terminal 6a of the LSI circuit 6 and utilizing the elastic deformation of the wire 10 secures a sure contact of the wire 10 to the terminal 6a. 
In the above-mentioned contactor using a spring pin, the wide range of the elastic deformation, from 100 μm to 300 μm, of the wire 10 (probe) secures a sufficient contact pressure. Additionally, in case heights of a multitude of the wires 10 vary to some degree, a sure contact is secured between each of the wires 10 and the corresponding terminal 6a. Also, a durability of the wire 10 is so superior to that of the anisotropic conductive rubber that the wire 10 can be used repeatedly one hundred thousand times approximately. Further, the wire 10 will not be deteriorated if put under a high-temperature condition as in a burn-in test.
As another example of a conventional contactor, there is a cantilever probing card. The cantilever probing card has a probe composed of such substances as tungsten. The probe is set oblique on a surface of a test board. The probe is of the size quite longer than the above-mentioned bent wire probe, providing flexibility to the probe under consideration. That is, the oblique arrangement and the flexibility of this probe give a sufficient elasticity so as to ensure a contact pressure.
The above-mentioned contactor using an anisotropic conductive material has the following problems to be solved: (1) a narrow range of an elastic deformation; and (2) a short durability.
(1) The Problem of a Narrow Range of an Elastic Deformation
A 200-μm-thick anisotropic conductive rubber has a narrow range of elastic deformation from approximately 25 μm to 100 μm. Therefore, if a terminal-containing surface of an LSI circuit is not flat enough, the narrow range of the elastic deformation cannot provide a sure contact. Thus, the LSI circuit has to have such a costly substrate as a ceramic substrate and a glass substrate having a flat enough surface. Additionally, with respect to such an LSI circuit as a wafer-level CSP using large solder balls, heights of the solder balls on a wafer vary by approximately 100 μm, with which variation the anisotropic conductive rubber cannot provide a sure contact.
(2) The Problem of a Short Durability
The anisotropic conductive rubber is extremely prone to deterioration in a high-temperature condition and, thus, cannot endure a repeated contact. Especially in a high-temperature condition (ranging from 125° C. to 150° C.) as in a burn-in test, a base rubber undergoes a plastic deformation and, thus, cannot endure repeated use. In response to this, the deteriorated anisotropic conductive rubber may be replaced, independent of a test board. However, an anisotropic conductive rubber usable for the size of wafer costs tens of thousands of yen per piece, raising a test cost for a wafer to be tested.
The above-mentioned contactor using a spring pin has the following problems to be solved: (1) an extremely high manufacturing cost; and (2) an irreplaceable contact pin.
(1) The Problem of an Extremely High Manufacturing Cost
A bent contact pin (probe) as shown in FIG. 2 is formed one by one by a wiring bonder. Therefore, in accordance with the number of probes to be formed, a manufacturing cost of a contactor increases. A wafer-level LSI circuit sometimes has as many as 50,000 terminals. In this case, a contactor has to have 50,000 probes correspondingly, extremely raising a manufacturing cost of the contactor. Additionally, a life cycle of a contactor is currently shortened to approximately 180 days, inevitably putting limits to repeated use of a contactor used in a lengthy burn-in test. For example, when a burn-in test requires 24 hours (a day) per wafer, a contactor can be used only 180 times approximately. Therefore, a depreciation expense of a contactor for a wafer becomes enormously high. Hence, such a contactor cannot practically be employed.
(2) The Problem of an Irreplaceable Contact Pin
When even only one of contact pins (probes) becomes damaged and unusable, the entire contactor also becomes unusable. As a matter of fact, in an LSI circuit test, it is difficult to completely keep a contact pin from being burned by a latch-up (overcurrent) in a burn-in test or from being damaged by a mechanical shock. However, since a contact pin is directly bonded to an electrode of a test board, it is difficult to remove a damaged pin from among other pins and re-form a new pin among the other pins. Therefore, a loss of only one pin may lead to spoiling an entire contactor and losing a huge sum financially.
Also, the cantilever probing card has a problem to be solved: a high impedance.
A contact pin of the cantilever probing card is ordinarily formed 20 mm to 30 mm in length in order to acquire a certain amount of elastic deformation. Generally, a pin of 20 to 30 mm in length has an impedance of 20 to 30 nH (nanohenries) and, thus, the entire probing card has large impedance. With the probe card having the large impedance, a high-speed test cannot be performed. For example, a device designed for an approximately 20 to 30 MHz operation can be tested with pins of 20 to 30 mm in length without a problem. However, a high-speed device designed to operate at more than 200 MHz cannot be tested at high speed because of the large impedance of the cantilever probing card.